Greetings Cosmic Americans!
From our perspective, slavery caused the Civil War. This is more or less apparent to anyone who cares to look at the documentary evidence from the secession crisis. Well, this notion is apparent for most of us anyway. There is of course a contingent among the good citizens of the United States who hold fast to the idea that the war was precipitated by some vague notion of protecting state rights - the blame for secession and the ensuing conflict thus resting squarely on the shoulders of tyrannical northern demagogues intent of preventing southerners from carrying out said rights...whatever they might be.
But the rest of us get it. As Abraham Lincoln said in his Second Inaugural Address on March 4, 1865, "All knew that this interest [slavery] was, somehow, the cause of the war. To strengthen, perpetuate, and extend this interest was the object for which the insurgents would rend the Union, even by war."
Fine. But over the past years, many of my students and a host of others have been puzzled by a salient notion: the overwhelming number of Union soldiers did not go to war to put an end to this rather conspicuous institution. If slavery threatened to destroy the country, as it seemed to be doing in a hasty fashion, why, in 1861, were northern soldiers not intent on destroying the cause of this mighty scourge? As the detractors of the "slavery as a cause" argument will happily tell you, (most) Yankees set off to war thinking very little of freeing slaves. Could one then conclude that northerners at arms did not believe that the war was over slavery?
This logic is about as convoluted as it gets - yet I hear it all the time (it's right up there with the idea that the war could not have been about slavery because most Confederates did not own any slaves). While it is certainly true that Union soldiers fought overwhelmingly to preserve the nation (see Gary Gallagher's The Union War on this one), they did so knowing full well (or at the very least - perceiving) that a "slavocracy," as they would have called it, was hell bent on destroying the republic. Abolitionists - those who sought to destroy slavery from the very beginning - were a tiny minority. Generally speaking, as the war went on, soldiers saw emancipation as a means to an end - in effect freeing slaves as a crippling blow to the Confederate war effort. Only when the war was over did Union veterans hail emancipation as (one of) the war's great causes. Their celebratory efforts were full of nods to freedom and Union.
But despite the changing nature of how Union soldiers warmed to emancipation, they could certainly tell you what the war was all about. As Union general Carl Schurtz wrote in his memoirs, loyal soldiers of the republic knew all along that slavery was indeed the "guilty cause of the whole mischief."